Deprecate onFID() and remove previously deprecated APIs

[tunetheweb]

Makes the following changes assumiong the next release after this merge is a major version bump:

• Removes old deprecated APIs (getXXX calls and ReportCallback)
• Marks onFID as deprecated and to be removed in next major version
• Removes polyfill base builds as per Consider deprecating base+polyfill due to complexity and misuse #238 (note this includes NavigationTimingPolyfillEntry)
• Updates all examples in README from onFID to onINP
• Updates INP to a CWV in README
• Notes FID as deprecated in README

Notable it does NOT:

• Remove the FID polyfill. It's need to emit a FID on bfcache restore as browser doesn't 😔
• Console.warn on onFID use. As we're in a handover stage I think it's a little early for that. We can add that in a few months without a major release IMHO.

[tunetheweb]

Test all now passing, but leaving this in draft until we're ready to merge, nearer 12th March. However I'm not planning on adding more to this PR so it is ready for review in the meantime.

[philipwalton]

Overall LGTM. I left a few suggestions in this PR. In addition, can you:

• Create a v4 branch and update this PR's merge target to that (instead of main).
• Remove references to the "base" script still in package.json (in "exports" and "files").

[philipwalton]

Still need to remove references to the "base" script in package.json (in "exports" and "files").

[tunetheweb]

Done!